Hard disk drive (HDD) and the like include, as a magnetic disk device, a magnetic disk provided therewith rotatably, and a magnetic head configured to write/read data to/from the magnetic disk. In HDD in the operation state, the magnetic head hovers on air current produced by the rotation of the magnetic disk and faces the surface of the magnetic disk with a slight gap therebetween.
When an external impact is applied to HDD, the impact may cause a concave or convex deformation in the inner periphery or the outer periphery of the magnetic disk. The deformation of magnetic disk changes the flying state of the magnetic head, and the magnetic head may contact the magnetic disk surface. In that case, the magnetic disk and/or magnetic head may be damaged.